Currently, many digital cameras have a zoom lens and a single image sensor to capture still and motion images. The captured images are then digitally processed to produce digital image files, which are stored in a memory in the digital camera. The digital image files can then be transferred to a computer and displayed, or transferred to a printer and printed.
Small camera size and a large optical zoom range are very important features of digital cameras. Users prefer to have a large zoom range rather than a limited zoom range. Unfortunately, providing a large zoom range lens, without sacrificing the quality of the captured images, increases the size of the digital camera. With higher-cost cameras, such as single lens reflex cameras, these problems are sometimes addressed by using multiple, interchangeable zoom lenses, such as a 28-70 mm zoom and a 70-210 mm zoom. Such an option, however, is inconvenient for a user of a compact digital camera.
Some digital cameras use one lens and multiple image sensors to produce a color image. Light from a target is separated into multiple colors by a prism beam splitter, and multiple monochrome image sensors are used to capture red, green, and blue color images.
Stereo film cameras and stereo digital cameras are known in the related art. These cameras have two horizontally separated lenses of identical focal length, which form slightly different images of the scene onto two frames of film or two image sensors. The two images provide a so-called “stereo pair.” The two lenses are designed to provide the same magnification, and both are used to simultaneously capture the left and right eye images on the image sensors in order to achieve a stereo effect.
In a compact digital camera, in order to obtain a large zoom range without incurring the cost of lens exchange, the digital camera is preferably equipped with multiple lenses having different focal lengths and the multiple lenses are used distinctively in accordance with a zoom position. When, for example, two lenses having different focal lengths are equipped on a camera, important factors include how the focal lengths are set and how the two lenses are switched, because a digital camera has, in addition to the optical zoom function, an electronic zoom function for electronically zooming digital image data.
Japanese Patent Laid-Open Publication No. Hei 10-42183 discloses a camera having one lens and one image sensor in which an angle of view is determined by driving an electronic zoom and an optical zoom, and a percentage of the optical zoom is increased while the angle of view is maintained.
Japanese Patent Laid-Open Publication No. 2003-283910 discloses a camera having an optical finder and a zoom finder wherein the finders are suitably switched and, when the finder is switched from the electronic finder to the optical finder, the lens of the optical finder system is driven in connection with the image capturing lens so that the angles of view match each other.
The above-described related art references relate to a camera having one lens and one image sensor and do not relate to a camera system having multiple optical systems for capturing images of a scene. Thus, none of these references discloses how the optical system is switched among the multiple optical systems.
Assume a digital camera having two lenses including a fixed focal length lens and a zoom lens. The switching of these two lenses is performed as follows. A focal length gap between the focal length of the fixed focal length lens and a minimum focal length of the zoom lens is interpolated by an electronic zoom of a digital image obtained by the fixed focal length lens. The camera is provided with a zoom-setting unit (zoom button) for setting a zoom position, and the user can set the zoom-setting unit to the wide side (wider angle) or to the tele side (narrower angle) so that the user can capture images at a desired zoom position. When the user sets the zoom setting unit provided on the camera to “tele,” the digital image obtained by the fixed focal length lens is electronically zoomed in, the lens is switched to the zoom lens when a tele-end of the electric zoom is reached, and the optical zoom is performed by use of the zoom lens. When, on the other hand, the user operates the zoom-setting unit to set the zoom-setting unit to “wide,” a digital image obtained by the zoom lens is optically zoomed out, the lens is switched to the electronic zoom of the fixed focal length lens when the minimum focal length of the zoom lens is reached, and the camera is zoomed out by use of the fixed focal length lens.
In a digital camera having two lenses, image capturing elements such as a CCD and CMOS are provided in correspondence to each lens. However, a structure for driving the image capturing elements using drivers provided in correspondence to the image capturing elements requires high power, and, therefore, may shorten a drive time of the digital camera using a battery. Thus, in a digital camera having multiple optical systems, an important factor for the user's convenience is to effectively drive the multiple image capturing elements.